Conventionally, electric vehicles (hereinafter referred to as “EVs”, which in the present specification are not necessarily limited to four-wheeled vehicles but also include two-wheeled vehicles, three-wheeled vehicles, and externally chargeable plug-in hybrid vehicles) are available.
The time needed to charge an EV is longer than the time needed to fill a gas tank of an internal combustion vehicle. Thus, it is expected that, with the prevalence of EVs, an increasing number of EVs have to wait for charging at charging stations. Thus, the EVs need information indicative of charging stations with few waiting EVs or recommended charging sites for users.
As conventional techniques, first, a traffic navigation system has been disclosed which informs an EV of optimum charging stations included in charging stations that can be reached by the EV and meeting predetermined conditions for the EV, based on a remaining battery level transmitted by the EV.
Moreover, a charging reservation server has been disclosed which allows the optimum charging station to be reserved by estimating the distance that an EV can travel based on the remaining battery level and history of traveling transmitted by the EV and searching for charging stations that can be reached by the EV.
Furthermore, a control system has been disclosed which invites those of the EVs managed by the control system which desire charging, assigns the EVs applying for charging to respective charging stations according to the power supply-demand balances of the charging stations, and guides the EVs to the respective charging stations.
The conventional techniques include some techniques for selecting an appropriate charging station for an EV and guiding the EV to the charging station. However, these techniques only determine a charging schedule for a single EV without taking the situations of other EVs into account.
However, public charging stations are shared by a plurality of EVs. In generally possible sharing forms such as a first-come-first-served basis and an order-of-reservation basis, the time needed to charge each EV, including a charging wait time for the EV, is closely related to times and places for the charging of other EVs. Thus, to determine an appropriate charging schedule for each of the EVs present within a certain road range, a technique is needed which selects an appropriate one of combinations of all the EVs with all the charging stations.